In biology and genetics, the germline is the population of a multicellular organism's cells that pass on their genetic material to the progeny (offspring). In other words, they are the cells that form the egg, sperm and the fertilised egg. They are usually differentiated to perform this function and segregated in a specific place away from other bodily cells.[1]
As a rule, this passing-on happens via a process of sexual reproduction; typically it is a process that includes systematic changes to the genetic material, changes that arise during recombination, meiosis and fertilization for example. However, there are many exceptions across multicellular organisms, including processes and concepts such as various forms of apomixis, autogamy, automixis, cloning or parthenogenesis.[2][3] The cells of the germline commonly are called germ cells.[4] For example, gametes such as the sperm or the egg are part of the germline. So are the cells that divide to produce the gametes, called gametocytes, the cells that produce those, called gametogonia, and all the way back to the zygote, the cell from which the individual developed.[4]
In sexually reproducing organisms, cells that are not in the germline are called somatic cells. According to this view, mutations, recombinations and other genetic changes in the germline may be passed to offspring, but a change in a somatic cell will not be.[5] This need not apply to somatically reproducing organisms, such as some Porifera[6] and many plants. For example, many varieties of citrus,[7] plants in the Rosaceae and some in the Asteraceae, such as Taraxacum produce seeds apomictically when somatic diploid cells displace the ovule or early embryo.[8]
In an earlier stage of genetic thinking, the distinction between germline and somatic cell was clear cut. For example, August Weismann proposed and pointed out, a germline cell is immortal in the sense that it is part of a lineage that has reproduced indefinitely since the beginning of life and, barring accident, could continue doing so indefinitely.[9] However, it is now known in some detail that this distinction between somatic and germ cells is partly artificial and depends on particular circumstances and internal cellular mechanisms such as telomeres and controls such as the selective application of telomerase in germ cells, stem cells and the like.[10]
Not all multicellular organisms differentiate into somatic and germ lines,[11] but in the absence of specialised technical human intervention practically all but the simplest multicellular structures do so. In such organisms somatic cells tend to be practically totipotent, and for over a century sponge cells have been known to reassemble into new sponges after having been separated by forcing them through a sieve.[6]
Germline can refer to a lineage of cells spanning many generations of individuals—for example, the germline that links any living individual to the hypothetical last universal common ancestor, from which all plants and animals descend.
https://en.wikipedia.org/wiki/Germline
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